Electrical frequency responsive device



2 Sheets-Sheet 1 A. W. DASCHKE ET AL ELECTRICAL FREQUENCY RESPONSIVE DEVICE Original Filed Jan. 7, 1955 Oct. 25, 1960 Oct. 25, 1960 A. w. nAscHKE ETAL 2,958,040

ELECTRICAL FREQUENCY RESPONSIVE DEVICE Original Filed Jan. '7, 1955 2 Sheets-Sheet 2 7 35 minlnv' m n T 6 of WMM .mf L Wd .L Wm h d@ AN United States Patent() ELECTRICAL FREQUENCY RESPONSIVE DEVICE Arthur W. Daschke, Morristown, and Nathaniel L.

Hooper, Towaco, NJ., assignors to J-B-T Instruments, Inc., New Haven, Conn., a corporation of 'Connecticut Continuation of application Ser. No. 480,421, Jan. 7, 1955. This application Feb. 10, 1958, Ser. No. 714,430

8 Claims. (Cl. 324-80) This invention relates to electrical equipment or apparatus in which vibrating reeds are utilized, and more particularly to vibrating-reed type meters.

The invention is lillustrated and described in connection with frequency meters; however, it should be understood that the invention is not limited to this specific use, since it has utility generally in the field of vibrating reed devices.

The present application is a continuation of our copending application S.N. 480,421, filed January 7, 1955, and entitled Electrical Frequency-Responsive Device, now abandoned.

An object of the invention is to provide a novel and improved, vibrating-reed type frequency-responsive device or meter which has increased sensitivity and accuracy in its response.

Another object of the invention is to provide a novel and improved, vibrating reed frequency-responsive device which has high eiciency and can operate on very low current `and voltage.

A further object of the invention is to provide a novel and improved frequencyresponsive device as above set forth, which is characterized by a high uniformity of performance when manufactured by production methods.

A still further object of the invention is to provide an improved frequency-responsive device in accordance with the above, which is of rugged and durable construction and not likely to easily get aout of adjustment.

Still another object of the invention is to provide an improved device as above outlined, wherein the effect of external magnetic fields is greatly minimized.

A feature of the invention resides in the provision of an improved frequency-responsive device wherein the pole pieces of the field structure are so constructed and arranged as to be in the closest possible proximity to the reeds.

Another feature of the invention resides in the provision of an improved device in accordance with the above, which is extremely simple in its construction and economical to fabricate.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

Figure 1 is an axial sectional view o-f a frequencyresponsive device in the form of a frequency meter, made in accordance with the invention.

Fig. 2 is an axial sectional view of the meter of Fig. 1, taken on a plane at right angles to the plane of the view of this figure.

Fig. 3 is a perspective View of the internal mechanism of the meter, sho-wn without the casing.

Fig. 4 is a face view of the meter.

Fig. 5 is a perspective view `of a modified form of interior meter mechanism or movement.

Fig. 6 is a top or plan view of the permanent magnet structure of the meter movement of Fig. 5.

The frequency meter shown in Figs. 1-4 comprises a casing 10, which may be of the usual cylindrical' construction having a mounting iiange 11 and a transparent face 12, and having a transverse rear wall or plate 13 on which the interior mechanism or movement of the meter is mounted. Behind the transparent face 12 a dial 14 is provided, carried by posts 15 which are secured in any suitable manner to the back plate 13. Also carried bythe plate 13 is a U-shaped frame 16 having inturned extremities 17 on which is mounted a driving coil 18. The frame 16 carries a mounting means 19 which supports a plurality of reeds 20 having different resonant frequencies, such as indicated by the scale S in Fig. 4. As shown in Figs. 1 and 3, the reeds 20 pass through the opening of the` coil 18 so as to be subjected to the magnetic flux set up thereby.

In accordance with the present invention an improved `field structure is provided, associated with the reeds 20 for the purpose of inducing a flux therein or polarizing the reeds so as to enable them to react sensitively to the flux of the coil 18. This field structure provides for a desirable accuracy of response of the reeds, and effects a high efficiency whereby the meter can be operated with but very little current consumption and heat. It further greatly minimizes the effect of external stray fields, provides for uniformity in production runs of instruments and is simple and economical to fabricate yet strong and durable in construction.

Referring to Fig. 3, this improved field structure cornprises a pair of elongate, coextensive north and south pole pieces 21 and 22 extending along opposite sides of the set of reeds 20, and comprises a pair of permanent bar magnets 23 and 24 attached to the extremities of the pole pieces 21 and 22 -and overlying opposite outer portions of the coil 18. The pole pieces 21 and 22 are preferably formed of flat strip stock such as silicon steel, and the bar magnets 23, 24 may be of the high coercive type formed of an alloy of aluminum, nickel and cobalt. The magnets 23, 24 may be attached to the pole pieces 21, 22 by any suitable means, as for example by soldering. Preferably, as shown in Figs. 1 and 3, the p'ole pieces 21, 22 are disposed against the fiat uper end of the coil 18 and are located closely adjacent the reeds 20, thereby to induce a magnetic polarity in the reeds. The field assembly thus provided may be so arranged as to have a press t with the upper end face of the coil 18, characterized by interlocking engagement, and may be made to snap in place if desired.

It will be understood that the reeds 20 are formed of magnetic material by which they will respond to magnetic fluxes. Thus, when an alternating voltage of frequency within the range of the instrument is applied to the coil 18, the fluctuating flux produced thereby will react with the induced iiux in the reeds, causing vibration thereof, and the reed whose resonant frequency is nearest to the frequency of the voltage impressed on the coil 18 will exhibit the greatest vibration, providing an indication of the frequency of the energizing current.

We have found, from actual measurements and comparisons, that by the provision of the field structure comprising the pole pieces 21, 22 located closely adjacent the reeds on their opposite sides, in conjunction with the permanent bar magnets 23 and 24 by which the pole pieces are polarized, a high degree of sensitivity and accuracy is produced in the instrument, together with greatly enhanced eiiiciency. The wattage consumed by the instrument is of a Very low value, and accordingly the heat created is of a small order of magnitude. But little current is required to actuate the reeds, admirably adapting the instrument for use with electronic and kindred equipment.

The magnetic field set up by the pole pieces 21, 22 is consistently uniform as between different instruments manufactured on a production basis, thereby reducing the necessity for individual calibrations and adjustments and.

insuringV reliability in use. The field structure, being 1ocated at the top end of the coil 18, influences the reeds 20 near their free ends where the reeds are able to respond mostreadilyto vibrating forces, and this feature enhances the sensitivity and efficiency of the instrument.

By virtue of the .pole pieces 21, 22 being closely juxtaposed to the reeds 20 a. screening effect is produced and there is thus minimized the likelihood of external fields affecting the readings of the instruments; therefore the accuracy ofthe indications may be relied on to a great extent in the presence of external strayiiux.

It will. be noticed that the field structure by which al1 ofthe above is accomplished is, however, extremely simple and requires but few components, enabling it to be produced' economically. Moreover, if for some reason the eld structure should become weakened, it may be readily removed and replaced without dismantling the entirev instrument.

Another embodiment of the invention is shown in Figs. and 6. In these figures, a frequency-measuring movement is shown comprising a driving coil 30 extending around a set of tuned reeds 31. Only three of the reeds 31 are shown for the sake of simplicity of illustration. However, it should be understood that a much larger number of reeds may be included in the set than is indicated by the showing. suitable block 32, which may be similar to the mounting block 19 shown in Figs. l and 3.

Extending along opposite sides of the set of reeds 31 are elongate, coextensive pole pieces 33 having upturned extremities 34 which are secured to permanent bar magnets 35. The assemblage of the pole pieces 33 and bar magnets 35 may be fastened to the end face of the coil 30 by brackets 36 as indicated. Thus the magnet assembly is disposed against the top end of the coil 30 and in close proximity to the free ends of the reeds 31.

As yclearly shown in Fig. 6, the pole pieces 33 have cutaway portions 37 by which the end portions of the pole pieces `are spaced apart a greater distance than the remaining portions. By this organization there is 'accomplished a uniformity of the field existing between the pole pieces, and therefore each one of the reeds 31 will be subjected to substantially the same field intensity, regardless of its position in the row or set. A high degree of sensitivity and accuracy is thus obtained over the entire range ofresponse of the instrument.

Variations and modifications may be made within the scope of the claims and portions of the'improvements may be used without others.

We claim:

1. A frequency-responsive device comprising a row of vibratable reeds disposed edge -to edge and having juxtaposed magnetic portions, said reeds being resonant at different frequencies and being movable in parallel paths the directions of which yare substantially at right angles to the line of extension of the row; a driving coil disposed `adjacent said reeds for magnetizing the magnetic portions thereof; and means inducing a steady magnetic iiux in the magnetic portions of the reeds, said means The reeds 31 are mounted on aY 4 including elongate, coextensive north and south pole pieces extending along opposite sides of saidy row of reeds and substantially parallel to the line of extension of the row, and including magnetic means disposed at both ends of the pole pieces and engaged with and bridging said ends, for polarizing the same with a north pole magnetism on one pole rpiece and a south pole magnetism on the other pole piece, said pole pieces and magnetic means constituting la completely closed, physical loop structure of magnetic material having opposed magnetomotive forces originating in the magnetic means, said reeds moving alternately toward yand away from said pole pieces when they are vibrating. l

2. The invention `as dened in claim l -inwhich the' means polarizing the pole pieces comprises a pair of bar magnets attachedto the pole pieces.

3. The invention as dened'in claim 2 in which the coil extends around the set of reeds, and in which the pole pieces and bar magnets are disposed at one end of the coil and extend in the directions of the convolutions thereof. n

4. The invention as defined in claim 3 in which the pole pieces and bar magnets are attached to and carried byan end'face of the coil.

5. The invention as defined in claim 3 in which the pole pieces extend across the end of the coil, and in which the bar magnets extend lalong opposite, outer sides of the coil.

6. The invention as defined in claim 3 in which the ends of the pole piece strips are bent at ian angle and overlie side portions ofthe har magnets.

7. The invention as defined in claim l in which the pole pieces comprise spaced strips, said strips being spaced further apart adjacent their ends than at points between the ends, thereby to make more uniform the field existing: between the strips.

8. The invention as dened in claim 7 in which the pole piece strips are flat and disposed edgewise to each other, and in which the greater spacing is effected by cut-back portions of the oppositely-disposed edges of the strips.

References Cited in the le of this patent UNITED STATES PATENTS 2,094,062 Darlington Sept. 28, 1937 2,201,836 McCune May 2l, 1940 2,356,229 Dunlap Aug. 22, 1944 2,403,809 Lingel July 9, 1946 2,429,094 Kent Oct. 14, 1947 2,435,487 Adler Feb. 3, 1948V 2,447,191 Lingel Aug. 17, 1948 2,681,588 Dyner June 22, 1954 FOREIGN PATENTS 868,470 Germany Feb. 26, 1953 868,635 Germany Feb. 26, 1953`- OTHER REFERENCES A new Idea in Vibrating Reed Frequency Meters, publication VF-43-l, copyright 1943, .LB-T Instruments, Inc., 441 Chapel Street, New Haven, Conn. 

